star trails

[FrankS]

I just got a Hasselblad SWC and I'd like to take a star trail photograph next weekend (hoping for a clear sky) when we will be visiting a friend's cottage.

I'm thinking f8 for 3 hours with iso100 film. Does that sound right for exposure?

(Doing a google search brings up lots of guides for digital cameras including stacking many images, but I'm using film.)

 

[Mackinaw]

I haven't taken star trail pics in years, but three hours is way too long. Try three minutes.

Jim B.

 

[ferider]

f8 @ iso100 sounds more like 15min or so, Frank. Result will strongly depend on how much light pollution you have. You can calculate the radial length of the trails, since you know that 360 degrees = 24h.

Have fun !

Roland.

 

[FrankS]

Hi Jim, I'm looking for circular trails, not a Milky Way type shot.

example http://en.es-static.us/upl/2014/03/star-trail-2-15-2013-Ken-Christison-NC.jpeg

 

[Tin]

hi Frank,


Use a large aperture. Use it wide open if you know that your lens will not give too much coma, vignetting, or other aberrations. Otherwise, just close it down one stop from maximum.

Go with 30 minutes, one house or longer. these exposures will create different lengths of trails. However, the governing factor is how dark you sky will be. Unless you have a very dark sky, fogging will occur with longer exposures.

Also with film, you'll also account for reciprocal failure.

Here is one link using on using film:

http://www.olegnovikov.com/technical/startrails/startrails.shtml

For a circular star trails shot, I'd say that you have to go to places like the desert or the far north. Otherwise, light pollution will ruin your photo.


Tin

 

[FrankS]

While there, I'll also try for a Milky Way shot with my digital camera and wide lens. Google search yielded an exposure recommendation of 30sec, f4, iso1600

Thanks also Roland and Tin for your responses.

 

[FrankS]

The plan for star trails is now several (increasing) exposures from 3 minutes to 2 hours.

 

[raid]

Good luck, Frank. Last time for trying such a setting was for me Halley's Comet. We drove outside Roanoke (Virginia) to find a place with hardly any city lights in sight.

 

[Mackinaw]

Hi Jim, I'm looking for circular trails, not a Milky Way type shot.......

My three minute comment was made in haste relying on my old-guy memory. I used to take a lot of 35mm star trail pics on Kodachrome back in the 70’s and 80’s. All were taken with the lens wide-open at F1.4. Two to three minutes gave me nice pics. Now that I think about what you’re asking, three minutes is way too short. Still, F8 at three hours will probably give you an overexposed pic.

You might want to try a series of tests using a digital camera set to an ISO of 100 and shooting at F8. The final product may not be a perfect match, but should put you in the ballpark for exposure.

Jim B.

 

[PhotoMat]

Frank:

For star trails with your Hassy, I would shoot at f/5.6 for as long as possible for good star trails (assuming a good, dark-sky site).

For the Milky Way shots, divide 500 by the focal length of your lens -- this will give the maximum exposure in seconds before the stars begin to noticeably trail in your photos. Using an 8mm lens on my APS-C sensor camera (Fuji X-Pro 2), most of my Milky Way shots are 40 sec. @ f/2.8 at ISO 3200.

 

[Spavinaw]

Star Trails-I was expecting pictures of where famous actors and actresses go hiking in the woods! Why not? 😛

 

[FrankS]

Nice Milky Way shot, photomat.

Does your formula (500/focal length) apply equally to all formats?

 

[rogue_designer]

As far as I know, the 500 rule is based on 35 mm full-frame, so convert to a rough equivalent (e.g. 80mm Hassy -> 43mm ish for 35mm diagonal equivalent)

 

[FrankS]

Thank you Liam. So my 38 on 6x6 is equiv to 20 in 35mm, so my safe time is less than 25 seconds. 🙂

 

[PhotoMat]

Rogue is correct -- the formula is based upon a 35mm equivalency. That being said, you should be able to shoot a maximum exposure time of approximately 22 seconds with your SWC without trailing becoming an issue.

 

[newsgrunt]

I've exposed TX320 for one/two hours wide open with the 40mm Distagon. Push processed. I wouldn't bother stopping down to f8. Wide open is still sharp af 😉

 

[FrankS]

I've exposed TX320 for one/two hours wide open with the 40mm Distagon. Push processed. I wouldn't bother stopping down to f8. Wide open is still sharp af 😉

It's puzzling that exposure info I've read on line are significantly different than your exposure data. (I know, I read it on the internet ...😉)

 

[michaelwj]

Hi Frank, nice to see the SWC is inspiring you!

For trails, the ISO and aperture needs to be sufficient to get a good star exposure within the 22 seconds for no trails. I thinks you might need faster film.
As the stars move, they will expose me next bit of film for 22 seconds and so on. You can then leave the shutter open for as long as you want, limited by the exposure in the dark sky, which will eventually overcome the stars.
Also, as the stars are always exposing a new piece of film, they're not going to be influenced by reciprocity failure past the 22 seconds, only the background.
I think you're going to have to be prepared to burn a few rolls of film to find out what will work. Of course we'd love to see the results!

 

[x-ray]

If you're going to shoot B&W I'd suggest Fuji Acros. Acros has the best reciprocity characteristics of all B&W films. Check Fuji for recommendations. To the best of my memory there's no correction for 1 minute exposures. Best bet is to check though.

 

[FrankS]

Hi Michael, yes the camera is an inspiration! I love this little problem of star trails exposure. 🙂 I love the way the camera's simple controls make it so easy to test.